Abstract
Electromigration-induced failures in integrated circuits have been intensively studied recently; however, electromigration effects upon interfacial reactions have not been addressed. These electromigration effects in the SnCu and SnNi systems were investigated in this study by analyzing their reaction couples annealed at 200°C with and without the passage of electric current. The intermetallics formed were ε-(Cu 3 Sn) and η-(Cu 6 Sn 5 ) phases in the SnCu couples and Ni 3 Sn 4 phase in the SnNi couples. The same intermetallics were formed in the two types of couples with and without the passage of electric current. The thickness of the reaction layers was about the same in the two types of couples of the SnCu system. In the SnNi system, the growth of the intermetallic compound was enhanced when the flow direction of electrons and that of diffusion of Sn were the same. But the effect became inhibiting if the directions of these two were opposite. Theoretical calculation indicated that in the SnNi system, the electromigration effect was significant and was 28% of the chemical potential effect for the Sn element flux when the Ni 3 Sn 4 layer was 10 μm thick. For the Sn and Cu fluxes in the SnCu reaction couples, similar calculations showed that the electromigration effects were only 2 and 4% of the chemical potential effects, respectively. These calculated results were in good agreement with the experimental observations that in the SnCu system the electric current effects were insignificant upon the interfacial reactions.